1. Field of the Invention
The present invention relates to an image processing circuit of an image input device which perform predetermined image processing, such as pixel interpolation, color transformation, contour correction, filtering, and culling, in the image input device.
2. Description of the Background Art
In general, a digital still camera (image input device) is constructed as shown in FIG. 33. Specifically, drive to a CCD 1 and image capture are performed on an image processing circuit 2. After a predetermined image processing, such as pixel interpolation, color transformation, contour correction, filtering and culling are performed on the image processing circuit 2, the obtained image is displayed on a finder of a liquid crystal monitor 3 or the like, and an image data is stored in a predetermined self-contained memory 4. If required, the image data is preserved and stored in a memory card 5, and outputted to a predetermined external processing device (personal computer) or the like, through an external interface (I/F) 6. In FIG. 33, there are shown photographing lens 7, aperture device 8, optical lowpass filter 9, infrared cutting filter 10, strobe 11 and power 12.
As shown in FIGS. 34 and 35, the image processing circuit 2 is often provided with, in addition to CPU 2a, a real time processing unit (RPU) 2b executing real time image processing of the image obtained by the CCD1. It is therefore constructed such that only the CPU 2a conducts a variety of image processing of the image temporarily stored in the self-contained memory 4. That is, processing conducted by a conventional real time processing unit 2b is limited to real time image processing solely for performing finder operation, and is completely separated from software processing. Thus, changes in processing steps are mere parameter changes in each block.
In this case, the real time processing on the real time processing unit 2b is completely separated from the software processing on the CPU 2a. Therefore, if required a special processing that is not prepared in hardware as the real time processing unit 2b, a real time processing is suspended temporarily, and executes the special processing is conducted, followed by other general processing. Since it is constructed such that the image temporarily stored in the self-containing memory 4 cannot be processed on the real time processing unit 2b, the succeeding processing is all processed by software, as shown in FIG. 35. In this case, a hardware processing block (namely, the real time processing unit 2b) is not used at all, that is, from the beginning to the end, processing is executed by software processing on the CPU 2. Therefore, if required a small exceptional image processing, processing speed lowers excessively and much time is required for processing, thereby causing disadvantages of loosing a chance of photographing, and the like.
Alternatively, on the assumption that software processing is executed from the beginning, the CPU 2a is speeded up for high speed processing. In this case, however, power consumption increases excessively due to the high speed operation of the CPU 2a, thus making it difficult to handle complicated processing contents.
From the foregoing, with the conventional method, image processing may not always be made at high efficiency.
An object of the present invention is to provide an image processing circuit of a digital still camera which enables to execute high speed image processing and minimize power consumption, by constructing so that a real time processing unit can resume high speed operation after that only part needed in software processing is corrected by a CPU.